<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  
</body>
<script src="js/全局污染.js"></script>
<script>
  // 解决方法：使用严格模式
  "use strict";
  // web is not defined
  // web 前必须有var

  var web="吼吼";
  //引入的js造成了全局污染
  show();
  console.log(web);
  
</script>
</html>